A well-known type of orthodontic appliance includes a plurality of brackets cemented to the labial surfaces of a number of the patient's teeth. The brackets are individually attached to an arch wire by elastomeric rings, wires or other such ligature means. Such components of common orthodontic appliances exhibit surface irregularities and pinch points which may rapidly traumatize the lip and cheek tissues overlying the appliance particularly after initial installation of the appliance in the mouth and following periodic adjustments of the appliance during the course of treatment.
This problem was recognized in Craven H. Kurz U.S. Pat. No. 4,512,740 issued Apr. 23, 1985. According to Kurz, a plastic shield placed frontally over an appliance would obviate irritation and soreness of the inner tissues of the cheeks and lips caused by rubbing against sharp appliance elements. Kurz discloses a shield which comprises an elongated arcuate member having a smooth labial surface and a plurality of lingually extending fingers which curve around the arch wire to position the shield in place in overlying relation to the brackets. However, in his specification, Kurz recognizes the need for supplementary means for securing his shield to the appliance. To this end, Kurz suggests that dental floss be threaded between the interproximal spaces of the teeth and tied to the shield to assure that it will remain in place over the appliance. This lack of positive attachment of the Kurz shield to elements of an appliance greatly reduces the utility and effectiveness of this shield construction. Thus, the task of tying the shield to the appliance must be repeated each time the patient cleans food particles from his teeth and the appliance after eating. Not only is this a substantial inconvenience and time-consuming activity, but the perserverance required to thread the floss between the teeth and to secure the thread about the shield and appliance would likely deter youngsters and other less determined patients from removing and reinstalling the shield as needed to maintain proper oral hygiene.
Not only do the fingers of Kurz inherently fail to provide positive and reliable shield attachment, but the fixed spacing between adjacent fingers of Kurz may or may not coincide with the intervals between a patient's brackets to permit each and every finger to engage the arch wire. Misalignment of any finger with an exposed arch wire segment would cause that finger to bear awkwardly upon a bracket and exacerbate Kurz's attachment problem. Therefore, it follows that use of fingers or other projecting attachment means with a shield of the Kurz type would require either customized patient fitting or provision of an impractical number of finger arrangements to accommodate the limitless variations in the size and shape of orthodontic appliances.
Another type of protective orthodontic shield known as "Hug Caps" is offered to orthodontists by Kreative Koncepts, Inc. of Hinsdale, Ill. This device is intended to cover completely the frontal portion of an individual bracket. Each shield comprises an elastomeric ring to which is attached an elastic cap which covers an underlying bracket to provide a smooth labial surface. The ring itself engages the bracket in a well-known manner serving as the actual ligature for securing the arch wire to the bracket. Individual caps are installed as needed on brackets by the use of a hemostat or like instrument. The manufacturer advises that special care be employed to avoid puncture of the cap membrane as the ligature ring is drawn over and about the brackets. The "Hug Caps" product has two principal drawbacks:
1. This device is intended to be installed by an orthodontist, not by the patient himself; therefore, office instruments and professional skill must be utilized to assure proper ligature installation and to avoid accidental damage to the shield and detachment or bending of the brackets.
2. It is likely that oral detritus will enter between the brackets and overlying cap membranes and that a serious oral hygiene problem will develop unless the caps are periodically removed to permit thorough cleaning of the caps and brackets. Such shield removal and subsequent reinstallation would require the patient to visit his orthodontist and incur an additional expense for the sole purpose of cleaning this type of shield. A. Kieth Amstutz et al U.S. Pat. No. 4,559,013 issued Dec. 17, 1985, points out the deficiencies of various prior art shields such as chamois or cloth inserted between the teeth and lip tissue, pliable wax strips pressed around braces to smooth over sharp edges and expensive thermoplastic protectors formed over the patient's teeth. Amstutz proposes an oral shield molded of silicone which covers completely the teeth and an attached orthodontic appliance wherein the molded indentations in the shield interfit with the teeth and the appliance to maintain the shield in place. The original expense involved in molding a shield about an individual patient's teeth and appliance remains a substantial deterrent to widespread use of custom fitted shields. Since Amstutz relies entirely on the interfit of the molded shield indentations with the appliance elements to secure the shield in place, it follows that a costly new shield might be required each time an appliance is substantially adjusted during the course of orthodontic treatment.